Rail flaw detector mechanism



Feb. 16, 1960 I D c w L 2,925,552

RAIL FLAW DETECTOR MECHANISM Filed Nov. 29, 1957 4 Sheets-Sheet 1 FIG}.|

I9 ll 30 27 23 l FIG. 2A F IG.2B

(RATIO A) (RATIO B) 'UPPER A2 LOWER GROUP GROUP E/ I m3/ RI r m m 7|CENTER GROUP OUTSIDE con.

F|G 2C (RATIO c) CENTER GROUP OUTSIDE con.

Feb. 16, 1960 G. DE G. COWAN ETAL 2,925,552

RAIL FLAW DETECTOR MECHANISM 4 Sheets-Sheet 2 Filed Nov. 29," 1957,

Feb. 16, 1960 G. DE G. COWAN EIAL 2,925,552

RAIL FLAW DETECTOR MECHANISM Filed Nov. 29, 1957 4 Sheets-sheaf 3AMPLIFICATION AND RECTIFICATIONI I OLATI N 1 "g.

con.

ARRANGEMENT FOR RAno'h".

1960 G. DE G. COWAN ETAL 2,925,552

RAIL FLAW DETECTOR MECHANISM Filed Nov. 29, 1957 4 Sheets-Sheet 4 mmhzmoe 2,925,552 RAIL FLAW nn'rncron MECHANISM Application November 29,1957,Serial No. 699,545

6 Claims. (Cl. 324-37) This invention relates to rail flaw detectormechanisms, and more particularly to the type of detector mechanismemployed on the Sperry 'rail flaw detector car. This car operates uponthe principle of energizing the rail with flux, as, for instance, bypassing direct current through the rail to establish an electromagneticfield surrounding the same, and exploring said field by inductive meansto discover any irregularities caused by the presence of internalfissures or other discontinuities in the rail. Such irregularities willcause the inductive means to generate an which, after being suitablyamplified, may be caused to operate an indicator, such as a recorder,within the car and a paint gun for marking the rail with paint in theregion of flaw.

The particular problem which presents itself here arises from the factthat variations in the electromagnetic field surrounding the rail aresetup not only by internal fissures which it is the function of themechanism to detect, but also by surface irregularities, such as'burns,shelly rail, flowed rail and slivers, which are not detrimental to theuse of the rail and which it is" not the object of the car to detect...

United States PatentO The operator withinthe car, seeingthe indicationupon the recording tape and the rail. must therefore use his i ownjudgment derived from viewing the-rail from the car to determine whetherthe mark has been caused by a surface defect or by an. internal fissure.Frequently this results in many unnecessary stops of the .car for thepurpose of hand testing the regionwhere indications are made.

It is therefore the principal object of this invention to provide amethod and means which: may be employed on detector cars of the Sperrytype which will enable an operator to distinguish between the types ofdefect which it is desired to detect from those defects which it isdesired to eliminate from the indicating mechanism.

Further objects and advantages of. this invention will- Fig. l is a sideelevation of. a portion of a rail fissure detector car having thisinvention applied thereto;

Fig. 2A is a vertical section through a rail head showing indiagrammatic form one arrangement of detector coils for distinguishingbetween certain typesof internal rail defects and certain types ofsurface defects.

Figs. 2B and 2C are views similar to Fig. 2A for distinguishing certaintypes of internal rail defects from certain other types of surfacedefects.

Fig. 3 is a block. diagram of the components of the invention. 7

Fig. 4 is a wiring diagram embodying the Fig; 2A arrangement of coils.

Fig. 5 is a wiring diagram similar to Fig. t'embodying the Fig. 2Barrangement of coils.

Fig. 6 is a view similar to Figs. 4mm 5 and-embody'- ing the Fig. 2Carrangement of coils.

Referring to Fig. 1 of the:drawings;there arez-shown y theelectromagnetic field, surrounding the rail, but said coils will alsorespond to variations in the field caused the parts of a standard Sperryrail fissure detector car which includes a car body 10 operating alongthe rails R. Fissure detection is accomplished by energizing the railwith flux by passing high amperage, low voltage current through eachrail from a generator 0 within the car body, supply current to spacedcurrent brushes 11 and 12 supported upon the current brush carriage 13which, when in lowered or effective position, is adapted to ride uponthe rails by means such as wheels 15. The current brush carriage 13 isnormally held in elevated or ineffective position by means of springs,not shown, and cable 16, but when it is desired to lower said carriage,fluid pressure, such as compressed air, is supplied to the cylinders 17to force out pistons 18 which are pivotally connected at 19 to thecurrent brush carriage 13. The current passed through the rail by way ofspaced brushes 11 and 12 will establish an electromagnetic fieldsurrounding the rail, and this field will be uniform except in theregion of flaw where it will be distorted. Such distortions of theelectromagnetic field are detected by a flaw responsive mechanism whichmay take the form of a plurality of induction coils supported in ahousing 23 at a constant distance above the rail surface by means of acarriage 24. Said carriage 24 is mounted on current brush carriage 13 bymeans of loosely fitting bolts 25 andsprings 26 to permit said carriage24, while riding on the rail on means such as wheels 27, to moveindependently of carriage 13 so that said carriage 24 may at all timesmaintain parallelism with the rail surface regardless of irregularitiesthereof. The induction coils withinhousing 23 normally cut the samenumber of lines of force, but on entering a region of flaw, they willcut a ditferent number of lines of force to generate an which .may be.caused to operate a mm P operating on a chart C (see Fig. 4) and toactuate a marking means suchas paint gun 30 mounted on the current brushcarriage 13 for spraying. the rail in the region of flaw with paint.

As stated in the introduction hereto, the inductive means will respondto variations in the electromagnetic field caused not only by thepresence of internal fissures which deflect the path of the current andtherefore vary by surface irregularities of the type enumerated in theintroduction hereto, i.e., surface burns, shelly and flowed rail, andslivers.

We have therefore devised the method and means to be describedhereinafter whereby we are enabled to distinguish between those trueinternal defects which we desire to' detect and various types of surfacedefects mechanism. Thus, the arrangement of coils shown in" Fig. 2A willdetect large and small transverse defects, large detail fractures,horizontal split heads and vertical split heads, but will not indicateengine burn fractures, engine burns andcentrally located slivers. Thearrangement shown in Fig: 2B will indicate detail'fractures, but

will not indicate large and small transverse defects, hon zontalsplitheads; vertical split headsengine burn fractures,.engine burns, shell,flow, centrally located slivers, The arrangement shown in" and largedetail fractures. Fig. 2C will indicate large transverse defects andengine burn fractures, but will not indicate small transversedefects,detail'fractures, horizontal split heads, vertical split heads, burns;-shell, flow. and centrally located slivers These arrangements may beused simultaneously, de-

pending upon the nature of the defects which are to be indicated oreliminated from the indication.

The principle involved in each of the forms Figs. 2A, 2B and 2C isthe'same. Referring first to'the form disclosed in Fig. 2A, there is alower group of coils A1 (here shown as five in number) spacedtransversely across the rail head, and an upper group of similar coilsA2 similarly positioned. \In this arrangement the ratio of signalvoltage response of the lower group of coils to the upper group of coilsis substantially lower when passing over an internal defect than whenpassing over asurface defect. Thus while the ratio when passing over aninternal defect may be on the order of 2:1, theratio when passing over asurface defect may be on the order of :1. It is this variation in ratiosthat makes it possible to distinguish between the types of defect whichit is desired to indicate and the types which it is not desired toindicate. One means by which this differentiation may be accomplished isdisclosed in Figs. 3 and 4. Here it will be seen that the lower group ofcoils and the upper group of coils each pass through an amplificationand isolation stage, after which they pass through a rectifier stage sothat only positive output is obtained. Thepositive outputs of each groupare combined, and each combined output is amplified by the separateamplifiers 41 and 42. The input to the amplifier 41 for the lower groupof coils A1 which produces the larger signal is reduced by feedback fromthe output of the amplifier 42 for the upper group of coils A2 to suchextent that the outputs from both amplifiers are the same when the coilspass over an internal defect of the type which it is desired to detectThus, although the'output of the lower group of coils to the upper groupof coils rnay be 2: l, suificient negative voltage'is fed back to thepositive input to the amplifier ofthe lower group so that the outputsfrom both amplifiers are the same. I This establishes that with a ratioof 2:1 (in the example chosen) there will be no differentialoutputbetween points 43 and 45. The degree of feedback may be controlledby potentiometer 44. Theoutputs from the two amplifiers 41 and 42 willplace simultaneous positive voltages on the twin grids G1 and G2 of thecoincidence thyratron 46, causing it to fire and operate the pen P onthe moving'chart C. The actuation of pen P breaks the circuit throughthe thyratron at47. v

Inthe example chosen, it was assumed that the ratio 2:1 was the desiredratio at which the pen should be operated as indicating aninternaldefect. If the ratio were greater or less than 2:1 the outputsof the two amplifiers would not be the same and there would be adifierential at points 43 and- 45. This differential voltage would berectified by a full wave rectifier and amplified by a third amplifier53. Since the output from the rectifier is positive, the output from theamplifier 53 is negative, and

46 to prevent firing of the thyratron. Thus, only when the selectedratio (in this case, 2:1) of output voltages ofthe lower and upper coilsexists can the pen P be 0perated. However, the ratio of lower to uppergroups of coils in response to internal defects varies within aspecified range, and cannot be limited to a single ratio. To obtain suchrange there is provided a range adjustment whereby the negative voltagewhich would be applied to the grid G3 is neutralized to any desiredextent, thereby providing a range of any desired extent within which thethyratron will fire. For this purpo se a potentiometer 55 4 lattertherefore will continue todevelop negative voltages on grid G3 toprevent actuation of the pen P, but ratios within the preselected rangewill be indicated on the chart. As stated hereinbefore the arrangementof coils shown in Fig. 2A is particularly adapted for detecting largeand small transverse defects, large detail fractures, horizontal splitheads and vertical split heads, while eliminating from the indicatingmeans any response due to engine burn fractures; engine burns andcentrally located slivers. The principle described h'ereinbefore may beapplied to other arrangements designed to 'give indications for certainconditions while eliminating indications due to other conditions. Thusin Fig. 128 there isshown an arrangement which will indicate detailfractures, but will not indicate large and small transverse defects,horizontal split heads, vertical split heads, engine burn fractures,

engine burns, shell, flow, centrally located slivers, and

large detail fractures. The same principle of utilizing two groups ofdiscretely located coils, one adjacent the type of defect which it isdesired to locate and indicate, and the other located remote therefrom.The ratio of response of the first group relative to the second group inthe presence of the desired defect will be smaller than the ratio ofthese groupsin response to other types of defects. Thus in Fig. 2B it isdesired to locate detail detail fractures-a type of defect which isfound in the region of the upper curved edges of the rail section.Therefore one group of coils B1 is located with the axis of each coilsubstantially normal to the curved edge, in which position these coilswill yield the maximum response in thepr'esence of a detail fracture. Asecond group of-coils B2 is positioned substantially parallel to theupper surface of the rail jbetween the coils B1 and spaced fromthe'latter coils; By' these arrangements a detail fracturewill givea lowratio of response of coil B1 to coils B2B Defects other than detailedfractures however-will give a-rnuch higher ratio of response of coil B1to coil B2.

Therefore-substantially the same electrical system-dis,

closed in Fig. 4 for the form' of-inve'ntion shown in Fig. 2A'may*be"employjed for'the-form'of invention shown in Fig;-2B,necessitating, as shown in Fig. 5, only the substitution of coils B1 forcoils A1 and of coils B2 for coils A2. The operation of the system fromthis this negative voltage is applied to grid G3 of the thyratron drawsa desired portion of the sum of the voltages at '43 i and 45 and appliesit as a negative voltage to'a fourth amplifier 56 whose positive outputis opposed to the negative output of' the third amplifier 53 .torenderthe grid G3 ineffective within the desired'range. f Thus, the

ratios of lower coils to upper 'coils which will indicate may be from1.5 :1 to 3:1,, this range still being substantially different from theratios due to surface defects. :The

point on-is the same as in Fig. 4 arrangement, the ratio adjustmentbeing set by the potentiometer 44 at whatever the desired ratio may beand the range adjustment being set by potentiometer 5 5. Thus onlydefects occurring within the desired range of ratios will operate thepen P to indicate a detail fracture'while all other responses will beeliminatedfrom the'indicating means. 1 a

'Another application of the principle is disclosed in Fig. 2C. Here -itis desired to indicate large transverse defects and engine burnfractures but it is desired to eliminate small transverse defects,detail fractures, horizontal'split heads,-vertical' split heads, burns,shell, flow and centrally located slivers. Forthis purpose there isagain employed two sets of discretely located coils, one set highlyresponsive to large transverse defects and engine burn fractures, andthe other set'less responsive to such defects. Therefore there isemployed a set of coils C1 substantially parallel to the upper surfaceof the rail and coacting with the central portion thereof, and a secondset of coils C2 positioned with their axis substantially v by merelysubstituting coilsQCl for coils A1 and coils C2 F t for coils A2.- Theratioadjustment'44 is employed as before as well as the range"adjustment 55, whereby only responses within the set range of ratioswill operate the indicating means but all other ratios outside the setrange will yield no indication.

Having described our invention, what we claim and desire to secure byLetters Patent is:

1. A rail flaw detector mechanism comprising means for energizing therail with flux and a plurality of inductive means spaced from the railand movable rela tive thereto so as to respond to variations in flux andgenerate signal voltages, said inductive means generating signalvoltages in response to internal rail flaws and to surface defects, oneof said inductive means being positioned closely adjacent the region ofinternal rail flaw, the other of said inductive means being positionedrelatively remote from the region of internal rail flaw, whereby theratios of signal voltages generated by the first inductive means withrespect to the signal voltages generated by the second inductive meanswill be relatively low for internal rail defects and relatively high forsurface defects, means for combining the responses of said first andsecond inductive means in opposed relation whereby a ratio of responseis obtained, indicating means, means for actuating said indicatingmeans, and means for rendering said actuating means effective only inresponse to said relatively low ratios.

2. A rail flaw detector mechanism as specified in claim 1, includingmeans for varying said last named responsive means to vary the range ofratios to which it responds.

3. A rail flaw detector mechanism as specified in claim 2, in which saidfirst inductive means comprises a plurality of coils positioned acrossthe rail head between the outer edges thereof, and said second inductivemeans comprises a plurality of coils similarly positioned with respectto the rail head but at a greater distance therefrom than the coils ofsaid first inductive means.

4. A rail flaw detector mechanism as specified in claim 2, in which saidfirst inductive means comprises a plurality of coils positioned withtheir axes substantially normal to the outer edges of the raFl head, andsaid second inductive means comprises a plurality of coils positionedsubstantially across the rail head between the outer edges.

5. A rail flaw detector mechanism as specified in claim 2, in which saidfirst inductive means comprises a plurality of coils positioned acrossthe rail head between the outer edges thereof, and said second inductivemeans comprises a plurality of coils positioned outside the outer edgesof the rail head and having their axes vertical.

6. A rail flaw detector mechanism comprising means for energizing therail with flux and a plurality of inductive means spaced from the railand movable relative thereto so as to respond to variations in flux andgenerate signal voltages, said inductive means generating signalvoltages in response to internal rail'fiaws and to surface defects, acertain set of said inductive means being spaced from the railditterently than a certain other set-of said inductive means so that theratio of response between them is relat'vely low for internal raildefects and relatively high for surface defects, means for combining theresponses of said first and second sets of inductive means in opposedrelation whereby a ratio of response is obtained, indicating means,means for actuating said ind cating means, and means for rendering saidactuating means efiective only in response to said relatively lowratios.

References Cited in the tile of this patent UNITED STATES PATENTS2,472,784 Barnes et a1 June 14, 1949 2,531,413 Dionne Nov. 28, 19502,729,785 Keevil Ian. 3, 1956

